Oscillation system



May 7, 1935. w. E. BOWER OSCILLATION SYSTEM Filed June 22, 1952 2 Sheets-Sheet l INVENTOR.

WM) 8. $04M,

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ATTORNEY May 7, 1935. w. E. BOWER OSCILLATION SYSTEM 2- Sheets-Sheet 2' Filed June 22, 1932 INVENTOR. wen/u. 3, Dowe v, BY

ATTORNEY Patented May 7, 1935 UNITED STATES PATENT OFFICE (Granted under the act of March 3, 1883, as

amended April 30, 1928; 370 0. G. 757) My invention relates broadly to oscillator systems and more particularly to an arrangement of oscillator system in which the oscillations of a piezo electric device are maintained constant under control of the application of successive impulses of light directed against the piezo electric device. w

One of the objects of my invention is to provide a method for generating constant frequency oscillations which comprises suspending a piezo ehctrlc device in a manner by which the charges generated by the device may be impressed upon the circuits of an oscillator system for controlling thereby the operation of a light emitting system and subjecting the piezo electric device to the impingement of successive light impulses in true phase relation with the mechanical displacement of the piezo electric device for maintaining oscillations at constant frequency through the 20 oscillator system.

Another object of my invention is to provide a circuit for the generation of electrical oscillations under control of a piezo electric device wherein the piezo electric device is maintained in continuous vibration through the medium of light impulses directed againstthe piezo electric device in timed relationto the mechanical displacement of the piezo electric device.

Still another object of my invention is to provide a construction of oscillation system in which a piezo electric device is employed for exciting an oscillation circuit with means controlled by the oscillation circuit for maintaining the piezo electric device in continuous vibration through the medium of successively applied light impulses directed against the piezo electric device in exact phase relation with the mechanical displacement of the piezo electric device.

A further object of my invention is to provide 40 an arrangement of amplifiercircmts having an input system and an output system with connections between a piezo electric generator in the input system of the amplifier circuit and con nections between the output system of the ampliner circuit and the mechanically moving system for subjecting the piezo electric device to successive light impulses for establishing oscillatory currents through said amplifier system for delivery to an output device at constant frequency.

A still further object of my invention is to provide a system for generating oscillations including means for electrically driving a shutter mechanism for controlling the emission of light imr pulses directed against the piezo electric device in true phase relation to the mechanical displacement of the piezo electric device for establishing constant frequency oscillations'in electrical circuits associated with the piezo electric device.

Other and further objects of my invention reside in the arrangement of shutter control mechanism for light rays and the arrangement oi. piezo electric apparatus associated therewith as set forth more fully in the specification hereinafter following by reference to the accompanying drawings, in which:

Figure l diagrammatically illustrates an oscillator system embodying the principles of my invention; Fig. 2 illustrates the arrangement of the electrically driven shutter mechanism employed in the oscillator system of my invention; Fig. 3 schematically shows the piezo electric device employed in the input circuit of the oscillator system of my invention; Fig. 4 is an elevational view showing the suspension means for the piezo electric device employed in the system of my invention; Fig. 5 is a lateral cross-sectional view taken through the piezo electric device of my invention; Fig. 6 is a view illustrating a fragmentary portion of the shutter mechanism for the light control device employed in the system of my invention; Fig. 7 is a theoretical view illustrating the displacement of the electrical charges along the piezo electric device employed in the system of my invention; and Fig. 8 shows a modifled arrangement of the piezo electric device employed in the oscillator system of my invention.

If light rays fall on a polished surface, there is exerted between the reflecting surface and the source of light a definite force which is a function of the area of the polished surface, the reflecting coefficient of the polished surface and the intensity of the light impinging on this surface.

As a comparison of pressure developed by light rays, consideration may be given to the factthat the radiation pressure of sunlight is equal to 10- dynes/cm and the energy density of a 100 watt lamp at one meter distance is equal to 3 10- erg/cm which is equal to the radiation pressure in dynes per sq. cm. at this distance. From a determination of the 7 pressure in dynes/cm necessary'to deform a quartz bar of known thickness, as described more fully hereinafter, I have devised an oscillating system composed of a. quartz bar freely suspended in an evacuated chamber with means for keeping the bar in continuous vibration through the medium of pulses of light flux repeatedly directed against the quartz bar, which pulses are in a true phase relation with the mechanical displacement of the quartz bar.

Referring to the drawings in more detail, Fig. 1 shows a schematic arrangement of the system of my invention wherein reference character I designates the evacuated transparent glass chamber into which is freely suspended a piezo electric element termed the vibrating element 2. In the system of my invention, the vibrating element 2 is quartz SiOz. This vibrating element is suspended at its nodal lines of free transverse vibration. The nodal points are then situated about one quarter the length of the vibrating element from either end. In the particular embodiment of the invention illustrated herein, the vibrating element 2 is suspended from the walls of the evacuated chamber l as shown more particularly in Fig. 4 by four metal hooks 3 embedded in the walls of the glass tube as shown at 4. Attached to said hooks are two stabilizing coil springs 5. Two silk threads 6 are looped around crystal 2 and anchored firmly to the supporting hooks 4 through the coil springs 5 at the top thereof. Sound dampers such as coarsely woven fabrics, or felts, may be situated within the evacuated chamber to minimize sound reflections. If only one point of radiation energy is used in driving the vibrating member 2, then the member is highly polished over an area as indicated at I. The front portion of the evacuaatcd chamber l is recessed into a flat surface as indicated at 8, and the entire area of the glass member may or may not be coated with optical black, except where the light flux enters at 8.

The maximum piezo electric charges developed 1 on the vibrating member 2 when bending occurs,

are at A and C, Fig. '7 and are of the same magnitude and sign. These charges will be collected electrostatically by electrodes 9 and In of Fig. 1 and Fig. 3, which may be connected to the filament electrode of amplifier II along lead l2 of Fig. 1. The charges developed on the vibrating member 2 at the same instant of time of bending at B, Fig. '7 will be of equal magnitude, but of opposite sign to those developed at A and C, and are collected by electrode l4 and carried by lead [5 of Fig. l, which is then connected to the grid element of the first stage of amplification in amplifier l l in Fig. 1.

I have shown an amplifier comprising three stages of amplification constituted by electron tubes 26, 21 and 28 coupling through the coupling transformers 29 and 33. The cathodes of each of the electron tubes have been illustrated as being heated from separate sources of potential at 34. The plate potential for each of the tubes has been designated at 35. It is to be understood that the showing of separate potential sources is wholly diagrammatic and that a common source may be used for the power supply circuits of the oscillator. The output circuit of electron tube 28 in cludes the series connected driving windings 36 which actuate armature l6 for driving the armature I 6 at synchronous speed as determined by the frequency of the charges generated by the piezo electric crystal 2.

Mechanical excitation of crystal 2 may be accomplished in any of several ways, one of which is to bring the synchronous motor armature l6 up to synchronous speed, by an auxiliary means represented at IT, that is at such a speed that the number of shutter effects produced by the alternate poles and spaces of the armature l6 of Fig. 6 are equal to the free period of oscillation of the vibrating member 2. Since the resistive forces of air pressure have been removed to a negligible amount within the evacuated chamber I, the decrement of oscillations have also been reduced. This reduction is such that if a force of 3 x l0 dynes/cirr is applied through my system for .00025 of a second, a quartz bar of the dimensions used in the system of my invention would be deformed to 2 10 mm. If this initial amplitude is allowed to die away for 60 seconds, it can be shown that the decrement is quite negligible as compared to the primary displacement. If, however, successive light impulses are caused to act in phase with the mechanical displacement of the vibrating member during each half period or caused to act throughout the entire period; the vibrating member will take on successive increments in displacement, continually increasing until the restraining forces of the vibrating member are equal and opposite to those of the driving force. After which, the vibrating member will execute true sinusoidal vibrations of constant amplitude and the frequency of the vibrating member will be free from changes brought about by barometric pressure fluctuations.

At a time when the amplitude of the vibrating member has attained sufficient magnitude, the auxiliary driving force H to the synchronous motor I6 may be removed by disconnecting the clutch mechanism designated at I8 and the synchronous motor switched to the controlling system shown in Fig. 1 coupled to the amplifier II where I9 is the light source, 20 and 2| designate a lens system. 22 shows a light shielding diaphragm or aperture plate, and 23 and 24 are here indicated as simple totally reflecting prisms illustrative of a method to direct the pulsating light source from the shutter mechanism to the polished area I of the vibrating member 2 through lens 25. The phase relation of the voltage col lected at G and F of Fig. 1 as compared to the open or closed position of the shutter at T, may be shifted by reversing leads I5 and I2 to G and F, respectively. The amplifier may be any conventional voltage amplifying system.

The vibrating member 2 may be maintained in a state of vibrational equilibrium by other forms of light controlling devices. One or more beams of light may be so directed as to assist the vibratory displacements of the vibrating member 2. The vibrating member 2 may be suspended at three or more nodal lines for the production of its overtones or harmonics. The chamber l, instead of being evacuated may be filled with any gas or vapor (metallic or otherwise) at any pressure and the same held constant or varied in any manner for facilitating the operation of the oscillator system.

The vibrating member 2 may, instead of having a polished and highly reflective surface, have a highly light absorbing area at l, as shown in Fig. 8, and then instead of the radiation pressure being reflected, it is assumed totally absorbed, whereby the vibrating member 2 will be repulsed due to the difference in temperature existing within the immediate vicinity of the applied source and the surrounding area. The reaction of the entire system to this method of driving will then be the same as hereinbefore described.

The oscillations generated by the oscillation system of my invention are delivered to the ou put transformer 30 through primary winding 3| and impressed upon secondary winding 32 for delivery to any desired utilization circuit.

The oscillator system of my invention has been found to be highly eificient and consistent in its 7 operation, and while I have described my invention in certain preferred embodimentsl desire that it be understood that modifications may be made and that nolimitations upon my invention are intended other than are imposed by the scopeof the appended claims.

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without th Payment of any royalties thereon or therefor. v n I What I claim as new and desire to secure by Letters Patent of the United States is as follows:

1. An oscillator system comprising an electron tube amplification system including an input circuit and an output circuit, an induction motor including an apcrtured disc andan electromagnetic driving device, connections between the output circuit of said amplificationsystem and said electromagnetic driving device, an evacuated envelope at least a portion'of which is--transparent, at piezo electric device suspended at its nodal lines of free transversevibration within said envelope and connected inthe input circuit of said amplification system, and means controlled by said apertured disc of said induction motor for subjecting a. portion only of said piezo electric-device to the successive bombardment of light impulses .for establishing constant frequency electrical oscillations.

2, An oscillator system comprising in combination with an electron tube amplification circult having an input system and an output system, a rotary shutter mechanism, means in said output system for driving said rotary shutter mechanism, an evacuated envelope at least a portion of which is transparent, a piezo electric device suspended at its nodal lines of free transverse vibration electrically connected with said input system, and a source of light rays con trolled by said rotary shutter mechanism for subiecting a portion only of said piezo electric device to the bombardment of light rays from said light source in timed relation to the vibratory movement of said piezo electric device for establishing electrical oscillations through said electron tube amplification system. I

3. An oscillation system comprising an electron tube circuit having input and output connections, an induction'motor including an electromagnetic driving device anda rotary shutter mechanism, connections between said electromagnetic driving device and said output connection, a piezo electric device suspended at its nodal lines of free transverse vibration, connections between said piezoelectric device and said input connection, a light source disposed adjacent said rotary shutter mechanism, and means for directing impulses of light from said light source upon a portion only of one surface of said piezo electric device in timed relation to the vibratory movement thereof for establishing electrical oscillations through said electron tube circuit for continuously driving said induction motor and generating constant frequency oscillations.

4. An oscillation generator comprising an electron tube having input and output circuits, a piezo electric device suspended at its nodal lines of free transverse vibration connected in said input circuit, an electromagnetic actuator connected in said output circuit, a load circuit connected with said output circuit, a. rotary disc inductively driven by said actuator, said rotary discs having a, plurality of radially extending teeth thereon, a light source for dirccting'light rays thrown the teeth cm said disc, an optical system for directing the light rays controlled by the teeth on said disc for impingement against a selected area of said piezo electric device in timed relation to the vibratory movement thereof for establishing constant frequency oscillations in saidelectron tube circuit for delivery to said load circuit and for continuously exciting said electromagnetic actuator.

An oscillation systmn comprising an electron tube amplifier including input and output circuits, a piezo electric device suspended at its nodal lines of free transverse vibration in a position capable ofmechanical displacement, means controlled by the output circuit of said amplifier for subiectins a part ofsaid piezo. electric device to successive bombardment of light impulses in timed relation to the vibratory movement of said piezo electric device for the generation of constant frequency oscillations through said ampliher, and a circuit connected with said amplifier for delivering the said oscillations to a load.

6. In a system for generating oscillations, an electron tube amplifier. a piezo electric device suspended at its-nodal lines of free transverse vibration in a vertical plane and adapted for vibratory movement, electrodes disposed at spaced intervals along said piezov electric device, said electron tube amplifier including grid, cathode and plate electrodes, connections between certain of the electrodes on said piezo electric device and said grid and cathode electrodes of said electrontube. an output circuit connected with said plate andcathode electrodes, means controlled by said output circuit for subjecting a portion only of said piezo electric device to the successive bombardment of light impulses in timed relation to the vibratory movement of said piezo electric device for reinforcing the establishment of oscillations through the circuits of said electron tube, and connections toa load circuit for delivering constant frequency oscillations to a load from said electron tube amplifier.

7. In an oscillation generator, an evacuated envelope, a piece electric element resiliently suspended at its nodal lines of free transverse vibration in said evacuated envelope and disposed in a plane, means for directing successive impulses of light against a portion only of said piezo electric device in a direction substantially normalto the plane thereof for mechanically displacing said piezo electric device in timed relation to the normal vibratory movement thereof for reinforcing the generation of oscillations under control of A said ,picuo electric device.

*8. An oscillation generator comprising a piezo electric device, an evacuated envelope enclosing said piezo electric device, means for resiliently suspending said piezo electric device at its nodal lines of transverse vibration in a vertical plane subject to mechanical movement in accordance with the vibratory action thereof, a light reflecting area on one side of said piezo electric device, and means for subjecting the light reflecting area of said piezo electric device to the successive bombardment of impulses of light in timed relation to the vibratory movement of said piezo electric device for reinforcing the generation of oscillations by said device.

9. In an oscillation generator, an electron tube amplification system including an input circuit and an output circuit, a piezo electric device suspended at its nodal lines of transverse vibration in a vertical plane for vibratory movement and connected with said input circuit, a synchronous motor, an actuating device connected with said output circuit for controlling the operation of said synchronous motor, independent driving means connectible and disconnectible from said synchronous motor and connectible with said synchronous motor for bringing said synchronous motor up to synchronous speed and disconnectible when said synchronous speed is reached for subsequent control by said actuating device, said synchronous motor carrying a multiplicity of light shutters arranged in an annular path, a light source for directing light rays through the light shutter driven by said synchronous motor, and a system of prisms for bending said light rays to a position in which said light rays are impinged against said piezo electric device for reinforcing oscillations through said amplification system, and means connected with said amplification system for delivering the constant frequency oscillations to a load.

10. In an oscillation generator, an evacuated envelope opaque to light rays except for a light transparent aperture adjacent one side thereof, a piezo electric plate, means for resiliently suspending said piezo electric plate at its nodal lines. of transverse vibration in a vertical plane within said envelope normal to the axis of said light transparent aperture, an electrical circuit for sustaining oscillations under control of the natural frequency characteristics of said piezo electric plate, and means for directing successive impulses of light through said light transparent aperture in said evacuated vessel for impingement against the surface of said piezo electric plate in timed relation to the normal vibratory movement thereof for reinforcing the oscillationsof said piezo electric plate.

11. In combination a rectangular parallelepipedal piezo electric crystal, means for supporting said crystal along lines normal to the plane formed by the longitudinal axis and the axis of the least dimension intermediate the ends of said crystal, means for applying an intermittent light flux to said crystal near the center thereof normal to the plane formed by the longitudinal axis and the axis of the intermediate dimension, and means for collecting the electric charges generated by said crystal comprising at least two plates, one of which is positioned near the center of said crystal and another of which is positioned near one end thereof, both of said plates occupying a plane normal to the incident light flux.

12. A piezo electric device comprising at least two conducting plates arranged parallel to the greatest surface of a rectangular parallelepiped of piezo electric quartz and displaced longitudinally therealong, means for applying an intermittent light flux onto a portion only of said crystal on the surface thereof opposite to said conducting plates whereby the crystal is made to vibrate transversely and set up cyclically varying potentials on said plates.

13. The method of operating a rectangular parallelepipedal piezo electric crystal at the free transverse period of oscillation in which the nodal lines of displacement of the crystal are disposed at right angles to the longitudinal axis of the crystal and the axis along the least dimension of the crystal, which comprises supporting said crystal at said nodal lines of vibration, impressing a light beam on to a part only of said crystal lying between the nodal lines of transverse vibration and interrupting said light beam at the free transverse oscillation frequency of said crystal.

14. The method of operating a rectangular parallelepipedal piezo electric crystal at the frequency determined by its free transverse oscillation characteristics which comprises impressing a light beam on to a part only of one of the faces of said crystal in such a way as to transversely stress said crystal and generate electric charges therealong which vary in value longitudinally thereof and utilizing the electric charges generated along said crystal to concomitantly control the value of the light flux impressed upon said crystal in such phase with the deformation thereof as to cause said crystal to oscillate at its free transverse oscillation frequency.

15. The method of sustaining free transverse oscillations in a piezo electric crystal element supported at its nodal lines of free transverse vibration within an evacuated envelope which comprises subjecting a portion only of a face of said piezo electric crystal element to the successive bombardment of light impulses to set the crystal element into transverse vibration, deriving from the oscillating crystal element a potential which varies cyclically as a function of the vibratory displacement of the crystal element and operatively controlling the successive bombardment of said crystal element with light impulses at the frequency of the potential which varies cyclically as a function of the vibratory displacement of the crystal element.

16. The method of operating a piezo electric crystal having the conformation of a rectangular parallelepiped which comprises supporting said crystal along its nodal lines of free transverse vibration and impressing an intermittent light flux on a portion of said crystal normal to the plane defined by the nodal lines of free transverse vibration and intermediate of said nodal lines.

WARD E. BOWER. 

